In Not by Genes Alone: How
Culture Transformed Human Evolution, Peter J. Richerson and Robert Boyd
explore the issue of the interplay of nature (genes) and nurture (culture) in
determining the evolution of the human species. One may ask whether another book that deals with the nature vs.
nurture controversy can add anything to our understanding of human evolution.
The answer to this question is a resounding "Yes!" This is because the authors of the book do
not focus their attention, as so many others have so tirelessly done, on
separating the contributions of nature and nurture to human action. On the contrary, they rely on the metaphor
that nature is very much like a recipe whose ingredients are determined by nurture.
They treat culture as the glue that combines heredity and learning, and focus
on natural selection as a guiding factor for human evolution.

The authors build their claim of
the critical role of culture in human evolution by observing that culture is
what makes the human species different from other species. This rather
predictable way of setting the foundation for a discussion on human evolution
may shatter readers' expectations of a groundbreaking and original approach and
thus may discourage further reading.
However, those who venture through the pages of this tightly written
volume are sure to be pleasantly surprised by the originality of the authors'
discourse and their captivating analyses.
This is indeed the case of a book that should not be judged by its
opening remarks!

In the pages of this interesting
book, the authors address two critical claims in a bold but fact-based manner:

With respect to the first claim, Richerson
and Boyd present a wealth of empirical illustrations that point to the role of
culture in accounting for human behavior and that discount or minimize the role
of other external factors (e.g., economics, climate, etc.) and of heredity. One of the best illustrations of this rich
assemblage of data regarding the role of culture in shaping behavior is
presented at the beginning of the book. There, the authors make the case that
differences in people's beliefs and attitudes regarding personal honor can
account for differences in aggressive behavior between Southerners and
Northerners. They rely on an impressive
variety of evidence collected by Nisbett and Cohen (1996), ranging from
laboratory data to ethnographic facts, to support their assertion. For instance, the authors report statistical
patterns of homicide rates that illustrate that Southerners are more likely to
be violent than Northerners in situations that can damage a person's reputation
in his/her community (i.e., personal honor).
The authors claim that this curious contextual difference in homicide
rates is supported by a difference in the beliefs that Southerners and
Northerners hold about violence and the circumstances that can justify it.

The second claim embodies Richerson
and Boyd's most daring proposal. These
authors put forward the thesis that cultural (in addition to natural)
environments have shaped the survival of individuals in groups, thereby
affecting which genes are transmitted to the next generations. Interestingly, the authors do not deny that
the way human beings process environmental and personal information is shaped
by natural selection. They simply acknowledge that natural selection is
influenced not only by natural environments but also by cultural ones. Thus, culturally acquired variations in the
way Southerners and Northerners engage in violent acts can be assumed to have
been preserved across generations not only via direct learning of beliefs from
one generation to the next but also via natural selection.

Both claims rely on the concept of
"population thinking" through which Richerson and Boyd explain how
some beliefs and attitudes survive across time in some social groups and other
beliefs and attitudes simply disappear. This concept allows the authors to
generate an account of cultural evolution in which culture can rapidly bring
into being useful behavioral changes (adaptations to altered
environments). Thus, culture becomes,
in the view of the authors, a compensatory mechanism for the adaptations that
biology would need considerably more time to implement.

One of the most captivating aspects
of the book is its reliance on diverse domains of knowledge such as
Anthropology, Psychology, Political Science, Sociology, and Economics. The
authors navigate each domain skillfully and purposefully on a mission to select
evidence that can be used to test their claim that culture is a critical factor
in human evolution. As skillful scientists, they examine all the different
kinds of evidence objectively, whereas as clever writers they arrange their
findings into a sturdy edifice that can weather not only many assaults from
opposing parties but also the mere passage of time.

The book is unquestionably an
engaging read for scholars and students of human evolution. Notwithstanding the large number of
attention-grabbing examples that the authors rely on for their theoretical
arguments, the book can become a challenging enterprise for readers who are not
familiar with this area of knowledge.
Not surprisingly, the bibliography at the end of the book can provide
useful material for in-depth analyses of the claims that the authors put
forward and the facts that they select to support such claims. However, a solid background in the Social
Sciences is required to fully appreciate the authors' theoretical arguments and
their selection of supporting evidence.
Thus, this is not a book for novices in the field of human evolution.
Rather it is a step forward in a long-standing debate that is continuing to be
controversial and whose appreciation requires a great deal of prior knowledge.

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